Comparative petrogenetic investigation of Composite Kaçkar Batholith granitoids in Eastern Pontide magmatic arc—Northern Turkey

Abstract

The Pontides are an east-west trending orogenic belt which is subdivided into west, middle and eastern sectors according to their different tectonostratigraphy. The Eastern Pontides are represented by west-east-trending tectonic zones resulted from a common Mesozoic-Tertiary history, comprises dominantly of magmatic rocks. The magmatic belt in the Eastern Pontides includes a large batholith, termed the Composite Kaçkar Batholith (CKB) in which there are various granitic facies. The emplacement of CKB occurred in pulses between the Early Cretaceous and Eocene period during the development of the eastern Pontide magmatic arc and following collisional events. The members of the CKB are Dereli-Ş ebinkarahisar (Giresun) in the west, southern Araklı (Trabzon) in the middle and Kaçkar Mountain and its surrounding area (Rize) in the east. The plutons ranging from syenite through monzonite to granite are typically medium-high K calc-alkaline rarely tholeiitic and metaluminous I-type. The studied members of the CKB intrudes into the Late Cretaceous arc volcanics and are determined to be Late Cretaceous-Eocene (75.7 ± 1.55; 41.2 ± 0.89) in K-Ar age. The tectono-magmatic setting of the granitoids has been interpreted as an arc-related granitic suite, a post-collisional granitic suite and a post-orogenic granitic suite. Some plutons including mafic magmatic enclaves (MME) and K-feldspar megacrystals suggest magma mixing/mingling. HFS and LIL element geochemistry of the granitic intrusions also suggest that fractional crystallization, magma mixing/mingling and crustal contamination played an important role in the evolution of the CKB. All the data mentioned above show that the granitoids in the three different regions may have been derived from an arc, developed in response to the northward subduction of the northern branch of neo-Tethyan oceanic crust beneath the Eurasian plate in Late Cretaceous and a collision between the Pontide arc and the Anatolide-Tauride platform in Paleocene.

Titanite and zircon fission-track dating resolves successive igneous episodes in the formation of the composite Kaçkar batholith in the Turkish eastern Pontides

“…Topuz et al (2005) found an Ar/Ar age of 52 Ma for the Saraycık-Bayburt granitoid in the eastern Pontides. Yılmaz s¸ahin et al (2004) found middle Eocene amphibole KAr ages for a porphyritic granodiorite from the southern Araklı-Trabzon region in the eastern Pontides ( Fig. 1; Table 1).…”

“…The Asniyor leucogranite intrudes the Ç amlıkaya and Marselevat granitoids and constitutes the third intrusive pulse. The Ayder granitoid and Sasmistal microgranite belong to the fourth igneous episode; the Ayder unit intrudes the Ç ag layan Formation and the Marselevat Boztug et al 2003Boztug et al , 2004. Abbreviations in the upper left inset; NAFZ north Anatolian fault zone; EAFZ east Anatolian fault zone; BSZ Bitlis suture zone; DSFZ Dead Sea fault zone and Sırtyayla granitoids.…”

“…They comprise comprehensive volcanics and plutonics derived from magmatism related to the northward subduction of the _ Izmir-Ankara-Erzincan (IAE) ocean, part of the northern branch of the NeoTethys between the Eurasian plate (EP) to the north and the Tauride-Anatolide platform (TAP) to the south (S¸engö r and Yılmaz 1981;Bozkurt and Mittwede 2001). Structural (S¸engö r and Yılmaz 1981;Yılmaz et al 1997;Okay and S¸ahintü rk 1997) and apatite fission-track data (Boztug et al 2004) indicate that the ocean closed and the EP and TAP collided around the late Palaeocene to early Eocene. The main age constraints for the timing of arc magmatism between Samsun in the west and the Turkish-Georgian border in the east are founded on fossiliferous calcareous and pelagic limestones of middle Turonian to Maastrichtian age (Taner and Zaninetti 1978) that are interbedded with submarine volcanics (Fig.…”

“…1). There are several structural (S¸engö r and Yılmaz 1981;Korkmaz et al 1995;Yılmaz et al 1997;Okay and S¸ahintü rk 1997) and petrological studies of the granitoid and volcanic rocks (e.g., Eg in and Hirst 1979;Manetti et al 1983;Yılmaz and Boztug 1996;Aydın et al 2003;Boztug et al 2003;Yılmaz-S¸ahin et al 2004;Karslı et al 2004;Arslan and Aslan 2006) of the eastern Pontide arc magmatism and some radiometric age determinations ( Fig. 1; Table 1).…”

K–Ar ages of granitoids unravel the stages of Neo-Tethyan convergence in the eastern Pontides and central Anatolia, Turkey

“…The granitoid rocks of this subduction-related magmatism have thus far been considered to be a single unit with Late Cretaceous to Early Tertiary age (Okay and Şahintü rk 1997;Yılmaz et al 1997). However, some recent studies have demonstrated the existence of syncollisional and post-collison-related extensional granitoids as well as arc-related I-type, calc-alkaline intrusives (Boztug et al 2003;Yılmaz-Şahin et al 2004;Boztug et al 2006Boztug et al , 2007a.…”